The present invention generally relates to bodily fluid sampling devices and more specifically, but not exclusively, concerns a lancet integrated test element with a flexible test element that bends during lancing in order to allow a lancet to pierce the skin or other tissue.
The acquisition and testing of bodily fluids is useful for many purposes and continues to grow in importance for use in medical diagnosis and treatment, such as for diabetes, and in other diverse applications. In the medical field, it is desirable for lay operators to perform tests routinely, quickly, and reproducibly outside of a laboratory setting, with rapid results and a readout of the resulting test information. Testing can be performed on various bodily fluids, and for certain applications is particularly related to the testing of blood and/or interstitial fluid. Such fluids can be tested for a variety of characteristics of the fluid, or analytes contained in the fluid, in order to identify a medical condition, determine therapeutic responses, assess the progress of treatment, and the like.
The testing of bodily fluids basically involves the steps of obtaining the fluid sample, transferring the sample to a test device, conducting a test on the fluid sample, and displaying the results. These steps are generally performed by a plurality of separate instruments or devices. Performing these steps can be difficult for patients, especially for patients with limited hand dexterity, such as the elderly, or those suffering the affects of their condition, like diabetes. Diabetics suffer many symptoms that can make self-monitoring difficult. For example, diabetics can sometimes experience numbness or tingling in their extremities, such as their hands, and also wounds tend to heal more slowly for diabetics. In a typical procedure, the patient first creates an incision in the skin by lancing the skin with a lancet. In order to ensure that a sufficient number of capillaries are cut for supplying an adequate bodily fluid sample, the incision has to usually be deep, which can be rather painful for the patient. Often the incision still does not provide an adequate amount bodily fluid for the sample, and the patient then must resort to expressing the fluid from the incision. If during expression of the fluid the patient is not careful, smearing of the fluid can occur, which may result in rendering the sample useless. Once a sufficient amount of fluid collects as a droplet on the skin, the patient has to position a test strip over the site such that the test strip contacts and absorbs a sufficient amount of the droplet for testing. Usually the droplet of fluid is quite small, and patients, especially ones with hand motor control problems, may experience great difficulty in positioning the test strip so as to collect a sample from the droplet. As should be appreciated, patients can become frustrated by this procedure, and consequently, they may perform the test less often or may even quit testing altogether.
Recently, lancet integrated test elements, or LITs, have been developed in which a test strip is integrated with a lancet so as to form a single disposable unit. While these integrated units have somewhat simplified the collection and testing of fluid samples, there are still a number of issues that need to be resolved before a commercial unit can be implemented. One issue concerns the interaction between the lancet and the test strip during fluid collection. In one type of design, the lancet is fixed relative to the test strip and extends past the edge of the test strip. During lancing, the entire integrated lancing test strip is fired by a lancing mechanism to form an incision, and after forming the incision, the entire integrated lancing test strip is typically retracted from the skin so that the blade is removed from the incision in order to promote blood flow as well as to dull the pain.
With the lancet fixed relative to the strip, a number of difficulties in sampling the fluid are created. For instance, as noted before, the lancet typically extends from the test strip near the capillary opening for the test strip. At such a position, the blade of the lancet can interfere with the collection of body fluid by smearing the droplet of blood on the skin and/or by drawing blood away from the capillary channel. Further, the distance that the capillary has to be retracted is directly proportional to the length of the lancet blade that extends from the test strip. The greater penetration depth created by longer lancet blades usually increases the amount of blood that is bled from the incision, but the greater length of the lancet necessitates that the test strip be retracted farther away from the skin, which in turn can reduce the chances that the blood will be successfully drawn into the capillary channel of the test strip. Conversely, shorter lancets reduce the distance of the test strip from the skin, but shorter lancets normally produce smaller fluid sample sizes from the incision. Moreover, retraction of the entire integrated device is sometimes inconsistent, thereby leading to some undesirable consequences. If the integrated device is retracted too far from the skin, the capillary channel might not be able to contact the fluid droplet on the skin, thereby resulting in an incomplete test or insufficient sample size for testing. The fixed lancet can also interfere with fluid collection because the fluid will tend to wick up the lancet during fluid collection.
To alleviate some of these difficulties, LITs have been developed in which the lancet is moveable relative to the test element. In one typical design, the lancet is coupled to a test strip via a metal spring. After the lancet is fired and the incision is formed, the spring is used to retract the lancet from the incision. However, such designs still have a number of drawbacks. For example, the flexible nature of the spring can complicate manufacturing by creating greater component variance when aligning the lancet with the test element. Also, packaging and maintaining the sterility of the lancet and test strip is complicated by the spring. With the spring, the lancet can easily extend, which can lead to accidental cuts and exposure of the lancet. Moreover, forming the spring adds expense to manufacturing, and the spring can be prone to damage during handling. If the spring is damaged or the lancet is misaligned, the lancet might not fully retract, which can lead to a number of difficulties. For instance, part of the lancet might remain in the incision after lancing, which can be quite painful to the user. Even when the lancet does not remain in the incision, the lancet tip can still extend past the end of the test element so as to disrupt fluid collection. With the lancet tip extending past the end of the test element, the body or biological fluid, such as blood, will tend to first wick up the lancet, thereby wasting the fluid. Due to the rigid nature of the test strip, if the test strip is pressed too hard against the skin, fluid flow from the incision can become constricted. Thus, needs remain for further contributions in this area of technology.